Process of preserving wood



Patented Oct. 12, 1926.

UNITED STATES PATENT OFFICE".

PROCESS OF PRESERVING WOOD.

Io Drawing. Application filed Kay 6,

The present invention relates to thereservation of wood in the form forexamp e of poles, piling, railway ties, blocks and yellow pine timber ofvarious kinds "and the object of the invention is toprovide a novel andimproved process whereby the penetration of the preservative into thesap wood to the heart wood in the material treated may be effected morethoroughly and with less amount of preservative than has been possiblewith such processes as have been heretofore used or proposed.

Heretofore it has been proposed to fill the cells of the wood withcreosote oil or liquid preservative by submitting the wood directly tothe preservative under pressure, but such treatment would beunsuccessful commer-- cially as the high pressure that would be requiredto effect a thorough penetration of the sap wood of the materialtreated, or penetration of the preservative to the heart wood wouldinvolve the loss of an excessive amount of the preservative because ofthe highly absorptive properties of the sap wood, and any effort toavoid the loss of an excessive amount of preservative by using a lowerpressure would be unsatisfactory as the oil would only partiallypenetrate the sap wood thus leaving portions thereof untreated orinsufficiently treated and hence subject to decay or deterioration, andthe relatively low pressure of the preservative in the presence of thehighly absorptive properties of the sap wood would be insuflicient toinsure penetration of the oilto the heart wood. In other processes,heretofore used or proposed, the preservative oil injected into the woodhas been permitted to remain therein for the purpose of filling thecells thereof, but such a procedure involved the consumption or loss ofan excessive amounts of oil or preservative.

The present invention provides aprocess whereby thorough enetration ofthe preservative oil throug out the sap wood 15 attained withoutexcessive absorption of oil or preservative, so that the sap wood Wlllbe thoroughly preserved by the use of a minimum amount of oil and theavoidance of excessive absorption of the preservative oil in the sapwood enables a sufiiciently high oil pressure to be applied to the woodto 1nsure penetration of the oil to the heart wood. Moreover, theprocess provided'by the present invention enables a substantial amountof the preservative oil employed to treating wood for the 1925. SerialNo. 28,501.

so that the oil thus'recove'red may beused in a subsequent treatment ofthe wood which may be effected inorder, to seal the cells of the woodand thus prevent loss of the preservative oil injected by the previoustreatment, by leaching or evaporation.

The procedure preferably followed in reservation thereof by the processprovide by the present invention, which may be carried out with the aidof apparatus such as that commonly usedin the creosoting of wood asheretofore practiced, is substantially as follows: The charge of wood inthe form of poles, piling,"ties, blocks or timber is placed in a chambersuch for example as the cylinder commonly used in the creosoting of woodby other processes, and the Wood is seasoned or dried, preferably bysteaming in the cylinder, followed by the application of a vacuumpressure within the cylinder as is usually performed as a preliminarystep in the creosoting of wood by other well known processes. Thispreliminary treatment, or any equivalent thereof, is for the purpose ofdrying the wood as thoroughly as ossible and thus preparing the wood tota e up the preservative oil freely and to facilitate the penetration ofthe oil through the sap wood.

After the wood has been thus treated in the cylinder, it is subjected tothe action of an atmosphere of a gaseous medium produced for example byforcing air into the cylinder until it reaches a pressure of from 40' topounds per square inch, and while the wood is maintained under theinfluence of this compressed air, or without releasing the air pressure,the cylinder containing the charge of Wood under treatment is pumpedfull of creosoteoil such as that commonly used in other well knowncreosoting processes, or any other suitable preservative in liquid form,until the creosote oil or preservative reaches a'pressure preferably ofat least 150 pounds per square inch. The

charge of wood is maintained under the penetrating influence of thecreosote oil or preservative which submerges 1t substantially at thepressure thereof as stated, un-

til about 80 per cent of the total amount of creosote oil which the woodis to receive has, penetrated the wood, this being for examplecalculated according to the cubic feet of wood composing the chargeundertreatment, and the drop in the level of the oil in the treatingtank due to the penetration of the oil into the wood, as indicated by agauge which may be provided on the treat- 1ng tank. Creosote oil ispreferably used as the preservative, and it is introduced into thetreatin cylinder at a temperature preferably of a out 190 to 200 F.

After the wood has received the desired amount of creosote oil orpreservative under the treatment described, the creosote oil is drawnoff from the cylinder when it may be suitably stored for subsequent use,and a vacuum of about 15 inches of mercury is created within thecylinder containing the wood under treatment. The purpose and effect ofthis vacuum treatment is to remove all excess air from the Wood, andwhich if present would resist or impede the subsequent injection ofcreosote oil, to be presently described, and to remove with the air anysurplus oil or preservative, this vacuum treatment of the wood beingcontinued for a period preferably of at least 20 minutes. Uponcompletion of the vacuum treat ment, the treating cylinder containingthe wood under treatment .is again filled with creosote oil, preferablyat a temperature of 190 to 200 F. and pressure is applied to the oiluntil it reaches a pressure preferably of at least 110 lbs. per squareinch, and this pressure is maintained until a gauge readmg of thetreating tank shows that the wood under treatment in the cylinder andwhich is submerged in the body of'creosote oil therein has absorbed theremaining proportion of the total amount or charge of oil which it wasintended the wood should receive, which would be 20 per cent of thetotal charge when 80 per cent of the total charge was absorbed by thefirst treatment described above, allowing for the amount of oil which isabsorbed b the wood while the cylinder is being fille with oil. Thepurposes and effects of this second or subsequent oil injection are torefill the cells of the wood which were emptied of oil and air by thevacuum treatment following the first oil injection, to seal the cellsand thus exclude moisture, fungi and germs which mightcause decay of thewood, and to prevent the loss of the creosote or preservative oil byleaching or evaporation.

By submitting the wood to an atmosphere of a gaseous medium such ascompressed air, and applying the oil under pressure without releasingthe pressure on the air or gaseous medium, the minute cells or crevicesof the sa wood on the poles, ties, blocks or other odies of wood undertreatment become filled with such air or gaseous medium and hence thehighly absorptive properties of the sap wood are counteracted to asubstantial degree, so that the oil may be subjected to a high pressurewhich will insure its penetration throughout thesap wood withoutexcessive loss of oil due to the highly absorptive pro rties of the sapwood and the use of a hig pressure on the oil which thus made possibleenables the oil to reach into and penetrate to the heart wood.Penetration of the preservative orig throughout the sapwood and to thehea wood is thus attained by the use of a minimum amount of oil orpreservative, as the loss of oil due to the highly absorptive propertiesof the sap wood is reduced to a minimum byreason of the presence of theair therein atthe time the preservative oil is injected. g

The vacuum treatment which follows the first oil injection removes anyair remaining in the wood and it also removes from the wood any surplusor unabsorbed oil which will be carried or forced out of the wood withor in advance of the escaping air, this further economizing the amountof oil used.

-The subsequent or final injection of the cresote oil or liquidpreservative may be accomplished at a pressure less than that employedduring the preceding oil injection, as its purpose is to fill the cellsof the wood whichwere emptied by the vacuum treatment following thefirst oil injection, thus protecting the wood a-gainst the entrance ofmoisture, fungi, germs or other destructive media, and thecells aresealed so that loss of oil by evaporation or leaching is minimized orprevented.

The wood preserving process provided by the present invention enablespoles, iling, ties, blocks and other pieces of woo comprising more orless sap wood to be thoroughly treated with creosote oil or other liquidpreservative with the use of a mini- .mum amount of oil or preservative,the

highly absor tive sap wood being 1prevented, by the air ling it duringthe rst treatment, from taking up an excessive amount of the oil orpreservative, so that a sufficiently high pressure may be applied to thepreservative oil to insure its penetration into and throughout the sapwood and to the heart wood.

' I claim 1. The process of preservin wood which comprises submittingthe woo to a gaseous atmosphere at a pressure above atmosphericpressure, submitting the wood to the action of a li uid preservative ata pressure substantial above that of the gaseous atmosphere, t erebycoating the walls of the interior cells of the Wood with thereservative, removing the gaseous atmosp ere and surplus preservativefrom the cells of the wood, and then submitting the wood to a liquidpreservative at a pressure substantially above atmospheric pressure toseal the cells of the wood.

2. The process of preserving wood which comprises submitting the wood tocompressed air at a-pressure substantially above atmospheric pressure,submitting the wood to the action of a liquid preservative at a pressuresubstantially above that of the compressed air thereby-coating the wallsof the interior cells of the wood with thevpreservative, submitting thewood to a vacuum pressure, and then submitting the wood to a liquidpreservative at a pressure less than that at which the first plied toseal the cells 0 the wood.

3. The process of preserving wood which comprises submitting the'wood toan atmosphere of compressed air at a pressure substantially aboveatmospheric pressure, submerging the wood in a liquid preservative at apressure. substantially above that of the atmosphere of compressed air,maintaining such pressure on the liquid preservative until apredetetermined proportion of the total amount of preservative to betaken up by the wood has been absorbed thereby, then submitting the woodto a vacuum pressure at a sufiicient pressure and for a sufreservativewas apfioient period of time to remove air and surplus preservative fromthe wood, and then submerging the wood to a liquid preservative at asufiicientpressure and for a sufficient period of time to cause the woodto take up the remaining proportion of the total amount of preservatlve.

4. The process of preserving wood which comprises submitting the wood tocompressed air at a pressure of at least 40 pounds per square inch, thensubmitting the wood, without releasing such compressed air pressure to aliquid preservative at a ressure of at least 150 ounds per square inchuntil a predetermined proportion of the total amount of the preservativeto be taken up'by the wood has penetrated the same, then submitting thewood to a vacuum ressurewf about 15 inches of mercury r a period of atleast 20 minutesyand then submitting the wood to a liquid preservativeat a pressure of at least 110 pounds per uare inch until the remainingproportion o the total amount of the preservative to be taken up by thewood has penetrated the same.

' HERBERT D. HECKERT.

